The invention relates to a side-bar chain for infinitely variable cone-pulley transmissions. The chain comprises side bars constituting links as well as rocker pieces constituting pins (joint pieces) which connect individual chain links by extending into apertures of the side bars. The end faces of the rocker pieces transmit the friction forces between the friction pulleys and side-bar chain.
Such side-bar chains are known in many forms. By way of example, reference may be made to German Pat. Nos. 1,065,685, 1,119,065, 1,302,795 and 2,356,289. In those arrangements, the joint pieces are each formed by a pair of rocker pieces which bear on one another through mutually facing rocker surfaces. The joint pieces are shaped such that they connect with the side bars of their respective chain link through a rotational locking arrangement. The rocker pieces bear on the inner contour of the side-bar apertures over their entire surface. It also appears from these printed documents that the chains can be assembled in a double side-bar structure, as disclosed in German Pat. No. 1,065,685, or a triple side-bar structure as disclosed in German Pat. No. 1,119,065 and shown in FIG. 14 thereof, where the double side-bar structure, with greater intervals of the pairs of rocker pieces in the running direction is of narrower construction transversely of the running direction, while the triple side-bar structure, while resulting in greater width transversely of the running direction of the chain, on the other hand, renders possible a reduction in the intervals of the pairs of rocker pieces, that is a reduction of the chain pitch.
This chain pitch is important in several respects. Firstly, the number of articulation pairs of rocker pieces possible per unit of length of the chain and thus the number of their end faces, determines the friction force which can be transmitted between friction pulley sheaves and chain. Next the chain pitch considerably determines the behavior of the chain as regards noise, since the entry of the rocker pieces between the cone pulley sheaves involves an impacttype noise which becomes louder the greater is the chain pitch. Finally, in the case of a coarse chain pitch, the course of the chain in the looping arc between the cone pulley sheaves is substantially polygonal, that is to say has relatively sharp breaks in the force direction, which has an unfavorable effect.
For these reasons the chains of triple side-bar structure would appear preferable. However, these chains are seldom used in practice, since in comparison with chains of equal performance of double side-bar structure they display a width which is half again as great transversely of the running directions. Because of the correspondingly increased chain weight, this leads to increased loading by centrifugal force and moreover, by way of the increased distance between the cone pulleys, has an effect upon the structural size of the entire transmission. The avoidance of these disadvantages predominates by far in comparison with the matters discussed in connection with the chain pitch.
U.S. patent application Ser. No. 285,869 filed July 22nd, 1981, naming Manfred Rattunde and Walter Schapf as inventors and assigned to the assignee of the present application discloses solving the above-mentioned problem by modifying such a side-bar chain so that the chain pitch can be shortened considerably in order to achieve a smoother running of the chain, a higher force transmission capacity and a better polygon formation. For this purpose the rocker pieces of the rocker piece pairs bear against the radial end webs of the side-bar pertaining to their chain link at two abutment regions spaced from one another in the radial direction. The two abutment regions bound a recessed rocker piece surface facing the radial end web of the side-bar. The radial extent of the rocker pieces largely corresponds to the interval of the abutment regions.
Numerous practical cases occur, especially in industrial transmissions set up in working premises, where it is not the strength or power transmission capacity but the noise level alone which is of decisive importance. For example, upper limits for noise intensity are prescribed by the labor supervisory departments. Often the only way to meet prescribed noise standards is by the additional fitting of noise protection hoods, which in turn necessitates additional cooling measures for the transmission.